Jack Bogle, the founder of Vanguard Group Inc., has warned against the dangers of allocating money to smart beta funds, saying he’s wary of new financial instruments that haven’t been tested by a big shock in the market.

“Smart beta is the big new thing,” Bogle said via satellite at a London Business School event with the AQR Asset Management Institute. “I wouldn’t quite say it was stupid, but it makes claims that are beyond its ability to fill.”

The 87-year-old isn’t the first to criticize smart beta. Rob Arnott, chief executive officer of Research Affiliates LLC and a founder of the discipline, shocked the industry last year with a paper that warned that a bubble is forming in the funds. Many strands of the investing style succeeded only because of a stampede in popularity, and they are poised to crash, he wrote.

Arnott also said in a separate paper this month that while factor investing -- the circuitry behind smart-beta -- works well in theory, returns all but evaporate in most live portfolios. Researchers at Northern Trust Corp. even went so far as to develop a rating system for how closely the ETFs track their goal, due to the prevalence of so-called style drift in smart beta funds.

Even so, investor demand for lower fees is estimated to see assets in smart-beta funds swell to $1.2 trillion by 2019, according to Citigroup Inc. AQR Capital Management co-founder Cliff Asness said in a paper in April 2016 that Arnott’s conclusions were without merit.

“I wonder if we are not suffering from too much innovation,” Bogle said about the finance industry. “How many products are designed to make life better for investors or to make it better for the marketers?”

Bogle also cautioned against the “aggressive” levels of trading in exchange-traded funds, which today account for about 40 percent of buying in the U.S. market. He said it was better to buy and hold a traditional index fund, or TIF, which was much more stable during the financial crisis than ETFs.

“Beware of any strategy that is designed to beat the market over 50 years,” he said. “I wouldn’t do it. Why take the risk when in the end the market return is there for the taking?”